5-2

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Limits to Growth
Section 5-2
Flora
Limits to Growth
Limiting Factor – factor that causes
population growth to decrease
Ex:
– Competition
– Predation
– Parasitism
– Human disturbances
– Climate Extremes
Types of Factors
Density-dependent
Density-independent
Density-Dependent Factors
DDLF – limiting factor that depends on
population size
These factors become limiting only when
the population density reaches a certain
level
Usually occurs when population is large
and dense
Ex: competition, predation, parasitism,
disease
Competition
Can occur within species or between
different species
More individuals leads to depleted
resources
Less individuals leads to less competition
Predation
Populations are often controlled by
predation
Predator prey relationships – mechanism
of population control in which a population
is regulated by predation
Ex: page 126; figure 5-7
Parasitism
Organisms are similar to predators
Take nourishment at the expense of their
hosts
Density-Independent Factors
Affect all populations in similar ways regardless
of population size
Ex:
–
–
–
–
Weather
Natural disaster
Season cycles
Human activities
** Populations often show rapid declines in these
situations
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